Redmi K30s BM53 Replacement Battery 3.85V 4900mAh

Redmi K30s / M2007J3SC — 3.85V Li-Polymer Replacement Battery (BM53)

This is a 3.85V, 4900mAh Li-Polymer replacement cell for the Redmi K30s (model M2007J3SC). It fits directly into the K30s chassis and matches the original BM53 specification. Install it when the original cell no longer holds adequate charge or shuts the phone down unexpectedly.

• K30s / M2007J3SC fit: Both model designations refer to the same hardware — same battery bay dimensions (84.40 × 64.24 × 5.25mm), same 3.85V nominal rail, and the same BMS connector pinout. One cell covers both identifiers.
• Bench tested on actual hardware: We cycled the BM53 cell through charge and discharge on the K30s platform and confirmed the BMS handshake completed without fault codes. The fuel gauge IC accepted the cell and began tracking state-of-charge across the full voltage window.
• First-cycle fast charge protocol: On first use after installation, disable fast charging and run one full discharge-to-charge cycle at standard rate. This lets the fuel gauge IC map the new cell's discharge curve before Xiaomi's fast charge protocol pushes high current into an uncalibrated cell — skipping this step causes erratic percentage readings for the first several days.

Sudden shutdown at 20–30% on the replacement cell

A fresh BM53 cell can trigger abrupt shutdowns in the 20–30% range if the fuel gauge IC is still calibrated to the old, degraded cell's discharge curve. The IC expects a certain voltage at a given state-of-charge, but the new cell has a steeper voltage cliff at lower charge levels under modem or display load. The phone interprets the voltage drop as a critical fault and cuts power before the percentage reaches zero. One full discharge cycle — draining to automatic shutdown and charging back to 100% with fast charge disabled — resets the coulomb counter and eliminates this behaviour.

Phone will not power on after the replacement battery arrived in storage

Li-Polymer cells shipped in storage mode can sit below 3.0V by the time they reach the end user. The BM53's BMS includes an undervoltage lockout that prevents the cell from accepting a charge current if voltage per cell has dropped below approximately 2.5V — this is a protection circuit, not a faulty battery. Connect the phone to its original Xiaomi charger and leave it for 15–20 minutes without pressing the power button; the charge IC applies a trickle pre-charge current to recover the cell above the lockout threshold. Once voltage climbs past 3.0V the BMS releases, normal charging resumes, and the phone will power on.